Heated Seat Wiring

[Mollymoodoo]

Hi

I have updated the climate control from MK3 pre-facelift to facelift and everything seems to work fine except for the heated seats.

I used data from here thank to @Luke_Anderson

From here thanks to @Nathan Buffery

And here thanks to @Preee

Heated seats.pdf

I think I have it right in that The cable from pin 5 of the old switches left and right, go to pins 22 & 23. before I moved them I checked the cable whilst still on the old switch and it was reading ~ 5volts. On the new switch I'm getting barely 0.08v coming out of Pins 22 & 23 and I can't for my life figure out why and wondered if anyone could shed any light on this and perhaps what I could do next to check why it isn't working.

 

[Mollymoodoo]

Same with pin 21 VREF this is 0.05 also.

[Nathan Buffery]

I'm not sure you should be getting any voltage from pins 5 on the old switches as they carry the voltage/signal to your seat module. You should, however be getting voltage from the wires you took out of pins 4 on the old switches as this is the feed. I'm pretty sure this should be 12 volts. I know it sound stupid, but you didn't have your multi meter set on 1000 volts, when you re-measured pins 22 and 23. I only ask because I've made this mistake myself!

[Mollymoodoo]

Thank you for your reply @Nathan Buffery

Ha yes it got to the point where I did check my multimeter, even testing it on a known 12volt switched feed.

Where was pin 4 supposed to go sorry? I put pin 5 left to 23  and right to 22 and the Vref to pin 21 came from pin 1 of the internal temp  sensor that should be a switched 12 volt. I have traced this all the way from the battery to fuse 85 on the BCM, (same one the Nextbase camera is on) and there is power there although I haven't checked what voltage I just know my camera works fine. I was contemplating picking up the feed from elsewhere.

[Nathan Buffery]

According to the pre facelift wiring diagram, pin 1 on the switch is part of the switch illumination. It's the yellow wire from pin 4 on the switch that is the heated seats feed. This goes back to the BCM pin 17 on connection 8. I only know this because I had to run wires to my switch. I would imagine there is enough power on the illumination circuit to power the camera, but not the seats. 

[Nathan Buffery]

Ah sorry, I must read slower!!! Yes the wire that goes to the temp/humidity sensor is on the same circuit as the feed that goes to pin 4 on the switch.

[Mollymoodoo]

 

2 hours ago, Nathan Buffery said:

Ah sorry, I must read slower!!! Yes the wire that goes to the temp/humidity sensor is on the same circuit as the feed that goes to pin 4 on the switch.

So what could be stopping the seats from working do you think? Should I try picking up 12 volts from pin 4 of the prefacelift seat switch do you think, just in case there is an issue with the cable from the BCM that I'm using at the moment. Surely any switched 12 volt should work or am I completely misunderstanding the purpose of pin 21 on the facelift HVAC unit.

 

 

 

[Nathan Buffery]

Did you splice into the Blue and White wire on the humidity sensor? 

[Mollymoodoo]

Yeah but that one is only showing 0.05v at the HVAC unit and looking at the diagrams for the facelift seats it only appears to be asking for a 12 volt switched live. I could be absolutely wrong though as this really isn't my forte. I have attached the wiring diagram below

heated seats facelift.pdf

[Nathan Buffery]

I'm not sure about the facelift module, but I know the feed is a signal live only. So it comes out of the BCM and gets split to feed various things (the humidity sensor is one of them). The switches are variable resistors with 5 settings. 0=0, 1=7.71k, 2=6.39k, 3=5.17k, 4=3.87k and 5=2.61k. I'm not 100% sure what this does to the voltage, but this signal then goes to the seat module. The heated seats have a another live that is fed from the boot fuse box 34 & 35 and I'm pretty sure this is the actual power for the heated pads. 

So.....you could test the ohms from your module pins to see if you are getting the same resistance. Might be worth checking the fuses, as you may of blown one whilst working on them. 

 

[Mollymoodoo]

HI

I've checked all the fuses, they're all good. The next stop after the footwell fuse 85 is the temperature sensor. I appear to either losing voltage along that cable or something else has to happen to create a voltage down that cable. There is enough power at the fuse though to power the camera I installed. I'll check continuity down that length of cable.

Looking at the wiring diagram the yellow feeds the switch on the pre-facelift so I'm wondering if I can use them on the facelift although it's a feed from fuse 35 that goes to pin 21 on the facelift. It would be nice to know what goes on in the facelift module. I might also just check the relays make sure they are working, see if I can record them on my phone as I'm a one man band 🙂

[Mollymoodoo]

Today I tried feeding 12 volt from a different source and that didn't work, so I rewired the original wiring and rotary switch and that didn't work. So now I'm wondering if the relay at the rear has gone kaput. Is there a way of testing relay, I'm thinking putting 12 volts through the coil and seeing if it clicks. What happens to make a relay stop working? I'm wondering what it is that I could have done to make it stop working properly if that is the problem.

[unofix]

1 hour ago, Mollymoodoo said:

Is there a way of testing relay, I'm thinking putting 12 volts through the coil and seeing if it clicks.

Hi, the heated seat circuit is easy to test. Start by seeing if the heated seat relay will operate when you connect the BLUE wire between the BCM and heated seat Relay  to 0 Volt (ground).

See the attached diagram.

Connecting the wire to ground will force the relay to operate provided it has the 12 volt positive supply from Fuse PF6 (70 Amp).

Do the test and let me know what happens and I can probably help you find the problem

[Mollymoodoo]

Hi

Thank you, I'm slowly getting lost 😄

Forgive my lack of knowledge, I'm just finding my feet with all this. Would I take the wire off the BCM and ground it or could I trap a wire in pin 2 of the relay and ground that? Also the only fuse I haven't checked is PF6, where can that be found?

Sorry for all the questions, as I say I don't have the necessary level of knowledge.

[unofix]

3 hours ago, Mollymoodoo said:

Hi

Thank you, I'm slowly getting lost 😄

Forgive my lack of knowledge, I'm just finding my feet with all this. Would I take the wire off the BCM and ground it or could I trap a wire in pin 2 of the relay and ground that? Also the only fuse I haven't checked is PF6, where can that be found?

Sorry for all the questions, as I say I don't have the necessary level of knowledge.

Best to disconnect the wire from the BCM and then ground pin 2 of the relay. 

PF6 should be located in the engine compartment Fuse box. I don't think you will have blown it with out knowing, because it is 70 amp and you would have one hell of a fault to take that out. 

[Nathan Buffery]

Surely it's easier to check if you have a live at fuses 34 + 35 in the boot, when you put your ignition on. This would tell you if your relay was working or not. I think I'd be inclined to do this before laying upside down in the passenger seat trying to locate pins on the BCM!!!

I assume you had the heated seats working before you fitted the FL climate module? 

[Nathan Buffery]

Just another thought......I think you can control heated seat through your sync module. I was wondering if you need to enable this with Forscan within the climate module. You may be able to either switch it off and on in forscan or see the switch positions. 

[Mollymoodoo]

8 hours ago, unofix said:

Best to disconnect the wire from the BCM and then ground pin 2 of the relay. 

PF6 should be located in the engine compartment Fuse box. I don't think you will have blown it with out knowing, because it is 70 amp and you would have one hell of a fault to take that out. 

Thank you for your reply.

I take your point, 70amp is a big fuse to blow. I managed a 100amp on a bus once but that took a spanner connecting from the battery input direct to to the steel surrounding the whole shebang, that went with a pop.

I have a lot to do today due to being let down by certain people, so don't think me ignorant if I don't get this done for a few days.

[Mollymoodoo]

4 minutes ago, Nathan Buffery said:

 

 

2 hours ago, Nathan Buffery said:

Surely it's easier to check if you have a live at fuses 34 + 35 in the boot, when you put your ignition on. This would tell you if your relay was working or not. I think I'd be inclined to do this before laying upside down in the passenger seat trying to locate pins on the BCM!!!

I assume you had the heated seats working before you fitted the FL climate module? 

Hi Nathan

This makes sense to be fair. I never checked to see if there was power there, just for continuity on the fuses to make sure they were ok.

As above I have managed to be saddled with a bit of work today so please don't think me ignorant if I don't get this done for a few days.

[Mollymoodoo]

7 minutes ago, Nathan Buffery said:

Just another thought......I think you can control heated seat through your sync module. I was wondering if you need to enable this with Forscan within the climate module. You may be able to either switch it off and on in forscan or see the switch positions. 

I'm on Sync 2, will this still be possible? The switch on the HVAC control is lighting up and doing the necessary same with if I use the rotary switch. The difference between the two is I'm getting 0.08v as a reference through the facelift control so 0.06-7v down the feeds. With the rotary I'm getting  ~12v and between 9 & 7v down the feeds dependent on switch position.

I'll check the relay and voltages coming off both rear fuses. I take they are 12v to feed the elements with whatever current the seat module allows?

[Nathan Buffery]

6 hours ago, Mollymoodoo said:

I'll check the relay and voltages coming off both rear fuses. I take they are 12v to feed the elements with whatever current the seat module allows?

Yeah I'm pretty sure the seat module deals with different switch positions.

[Mollymoodoo]

Thank you Nathan, I will take a look at some point this week.

[Mollymoodoo]

Ok so it turns out that I have broken the drivers side  by connecting a live feed directly to the feed to the module by mistake, but I have got the passenger side working fine by connecting pin 4 from the  PFL heated seat plug to pin 21 in the FL HVAC unit to give the seats power. I'm not sure what the problem could be on the drivers side, possibly needs a new module as the fuses, which I have re-checked all seem to be fine. I'm not that fussed about the drivers side though as I never use it.

[Rowan112]

Hey Molly, Your post seems very interesting.

 

Did you replace your center console or just the climate control?

[Nathan Buffery]

9 hours ago, Mollymoodoo said:

Ok so it turns out that I have broken the drivers side  by connecting a live feed directly to the feed to the module by mistake

Oh no!! So do you think you connected the full 12v to the signal wire (terminal 5 on the PFL switch)?